A received signal power indicator (RSSI) function is an important function of a receiver in a microwave system. The RSSI function provides a real-time received signal power indicator and provides fundamental data input for a part of functions in the microwave system, for example, a determining function of determining, during network construction, whether a microwave device is correctly installed. There is an extremely high requirement on both accuracy and realtimeness of an RSSI. Accuracy of an RSSI is primarily reflected by whether a fluctuation range of an indicated RSSI indicator meets a requirement in a situation in which input power is stable, and realtimeness of an RSSI is primarily reflected by whether a result indicated by the RSSI can track and reflect a change of adjustment when power of an external input signal regularly fluctuates, for example, when strength of a signal is adjusted at a speed of 100 dB/s.
An adaptive bandwidth switching function needs to be supported in the microwave system. The adaptive bandwidth switching function means that, when rapid fading occurs in a spatial transmission process of a microwave, for example, phenomena such as an unexpected rain or fog may cause rapid fading of a transmission channel of the microwave, a reflection of which in a signal is a rapid drop of receive power at a receive end. In a narrowband system, a data stream has a low transmission speed and occupies a narrow transmission channel, while in a wideband system, a data stream has a high transmission speed and occupies a wide transmission channel. By using a characteristic that sensitivity of a narrowband system is higher than that of a wideband system, data stream bandwidth is switched from wideband to narrowband, thereby ensuring stable functioning of data with a high priority, where the data stream bandwidth refers to a manifestation of a rate of a data stream in the frequency domain, for example, data stream bandwidth of a data stream whose rate is 1 Mbit/s is 1 MHz.
In the prior art, an amplification unit performs amplification on a received data stream; an analog-to-digital conversion unit performs analog-to-digital conversion on an amplified data stream to obtain a digital data stream; a filter with constant filtering bandwidth is used to filter the digital data stream; a power detection module is used to perform power detection on a filtered digital data stream; an amplification control signal of the amplification unit is obtained according to detected power; and an RSSI value is obtained according to the amplification control signal, the detected power, and a relationship between filtering bandwidth and bandwidth of the digital data stream. A function of an amplification control signal is to perform amplification control on a data stream received by a receiver, and an amplification function needs to ensure stability of a filtered digital data stream. When signal bandwidth of the microwave system is switched, the amplification control signal transits. For example, total power of 100 M bandwidth at an analog-to-digital conversion unit is 1 W; filtering bandwidth is 10 M; actual bandwidth that can be detected by power detection is only 10 M, which is a tenth of 100 M; and at this time, power detected by power detection is 0.1 W. When the bandwidth is switched to 50 M and the power is still 1 W and the filtering bandwidth is still 10 M, power that can be detected by power detection becomes 0.2 W, and an amplification control signal obtained according to the power value transits until detected power is 0.1 W. At this time, actual power of 50 M bandwidth decreases to 0.5 W, while 0.5 W power affects operating of the analog-to-digital conversion unit, causing bit errors.